YES. I am almost always tired when I sit down to write because I write when my kids are in bed—so I’m either up early or up late. But I’ve learned that if I wait for the perfect moment to write, I won’t write very often. So I just try to write through it and usually it gets better as I go along.
Some things I’ve found that really help me clear my mind are: taking a break from the manuscript (for a few hours, a few days, whatever I need), starting a new fun project, going for a run, and hanging out with my kids or with a good friend.
Reverse psychology works on me too. If I tell myself I’m not going to write/I can’t write for a while, then it’s not long before I’m DYING to write!